1. The Field of the Invention
The present invention relates to supported nickel catalysts and to the manufacture thereof. More particularly, the invention relates to catalysts and manufacturing processes for making supported nickel nanocatalysts having high nickel loading (e.g., greater than 5%) and high metal dispersion (e.g., greater than 5%), as measured by hydrogen adsorption.
2. Related Technology
Supported elemental nickel and nickel oxide catalysts have wide applications in important reactions such as methananation, hydrogenation of fats and oils, hydrocracking, and hydrodesulfurization, among others. Improvements in nickel-based catalysts can lead to improved efficiencies in these processes, thereby reducing costs and/or increasing product output.
One technique commonly used to obtain supported nickel catalysts is to begin with the nickel atoms dissolved in a solvent. The nickel atoms are usually provided as nickel salts due to the solubility of nickel salts in various solvents. The support material is added to the nickel solution and the nickel is then precipitated onto the support, typically by adding a base. The supported nickel catalyst is then dried and calcined (e.g., at 375° C.) and activated by reduction with hydrogen.
It is known in the art that heating and/or calcining the catalyst atoms causes agglomeration of catalyst particles to some degree. Agglomeration is undesired because it reduces the performance of the catalyst. Agglomerated particles have less exposed surface area and are consequently less active for a given amount of metal (i.e., only the exposed metal atoms on the surface are available for catalysis). Despite the undesirability of agglomeration, exposing the catalyst to heat is often necessary to activate the catalyst or for carrying out the reactions that involve the catalyst.
The extent of agglomeration during manufacture or use of the catalyst typically depends on the size and number of catalyst particles. Smaller particles are more likely to agglomerate because of higher surface tension compared to larger particles. Higher metal loading also tends to facilitate agglomeration because the particles are in closer proximity. Although catalyst performance can in theory be increased with smaller catalyst particles, improvement in catalyst performance has been somewhat limited by the inability to beneficially increase metal loading while using small catalyst particles.